The present invention relates to a hand grip operated cord clamp for wiring devices and particularly which includes means for attachment of a hand grip to a wiring device in which electric conductors of a cable are secured and to a clamp associated with the grip for providing a strain relief clamping of the cable.
It is well known that caps and connectors are the common designation of wiring devices which are employed to provide terminals to cables which carry power from power sources to apparatus in which the power may be utilized. Such caps and connectors include means for fastening the conductors of cables to electric contacts of the caps and connectors and includes means for gripping the cable at its insulation adjoining the end of the cable from which the conductor extends into the cap or connector.
A U.S. Pat. No. 3,461,417 issued to the same assignee as this application discloses the structure of such a cap and connector and the metal clamp structure associated with the cap and connector for strain relief gripping of the cable end by its insulation. The cable clamps of such caps and connectors do not serve as convenient hand grips for the hand manipulation of the devices in making connection or disconnection between such devices.
There is a form of cap which is equipped with a set of straight blades and these straight blades are inserted into straight blade receptacle in a matching connector. Such a cap is disclosed in U.S. Pat. No. 3,624,591 and another form is disclosed in U.S. Pat. No. 3,744,008.
There is another form of cap which is equipped with so-called locking blades and use of such caps and connectors together involves an insertion of the blades into respective matching blade ports in the connector and the turning of the cap relative to the connector in order to lock the locking blades in place in the connector. Similarly, when the locked cap and connector are to be disengaged, the first motion which must be imparted to the cap relative to the connector is a turning motion opposite from the turning motion which locks the blades in place. This is followed by a pulling motion to remove the blades of the cap from the blade receptacles of the connector. A hand grip which is used in connection with such locking caps and connectors is therefore subjected to a rotary motion as part of the locking and also as part of the unlocking of the blades during the normal use and operation of such locking caps and connectors.
Based on simple caution in use of such electrical devices, it would not appear feasible to employ a cable clamp for a wiring device which operated by the turning of a hand grip where the operation of the wiring device as a cap or connector required the imparting of a turning motion to the same hand grip. In other words, it would not appear feasible to make a cable clamp operate by hand turning activation of the clamp where the turning motion applied to the hand grip portion of a cap or connector was the same motion applied to the same hand grip portion of the device which was necessary to operate the wiring device in breaking the locking connection with another wiring device. More conventional caps and connectors such as those disclosed in U.S. Pat. Nos. 3,605,059 and 3,457,980 do not employ cable clamps which are operated by application of a torsional force to the grip of the device itself.
It is somewhat surprising that it has been found possible to construct a device which provides a calmp about the cable to effectively lock the cable to the wiring device, and to provide a strain relief for any strain that is placed on the cable, by a torsional or twisting motion which is essentially the same twisting motion which is applied to the device as a whole when bringing them into their locked and unlocked positions.
In other words, it has been found that use may be made of a twisting motion to clamp a cord clamp by hand onto a cord and that use may be made of a reverse twisting motion in releasing the clamp from the cord where both motions are imparted by use of hand grip on the respective clamps. What is surprising is that this hand twisting of the clamp element can be successfully used in the clamping and unclamping while the hand twisting of the connector is employed in connecting and disconnecting the cap and connector from each other.
What is surprising is that although one might normally expect that it would be improvident based on safety consideration to construct a cord clamp for a cap and connector where the cord clamp itself is operated by a hand twisting motion to engage the cable in the clamp and also to disengage the cable from the clamp it has now been found that this can be done and that the clamp so constructed is highly effective for its purpose. This is contrary to the teaching for example of U.S. Pat. No. 3,865,461 which includes a ratchet and locking pawl to prevent undoing of the device during handling even where locking blades are not involved. A patent such as the Santologo patent shows tool flats indicating the need for tools in manipulating the device.